26 BOOK OF SPECIES. 
umbilicus peculiarly open ; aperture simple, most 
minute. B. T. 46. 
H. crystauutina. Minute, thin, perforated, 
depressed, white, shining, and diaphanous.  T. 
42>. 5: 
CAROCOLLA. 
Orbicular, more or less convex or conoid above ; 
circumference angular and sharp ; aperture 
transverse, contiguous to the axis of the shell; 
outer lip sub-angular, frequently dentated be- 
low. 
C. ALBILABRIS. Imperforate, convex on both 
sides, chestnut-brown, with a paler obsolete band 
on the keel ; six obliquely and slenderly striated 
whorls; aperture transverse and ear-shaped, with 
a white reflected lip. W. 33. 34. 
C. tucerna. Orbicular, umbilicated, and 
somewhat depressed, smooth and whitish; lip 
reflected, with two teeth in the inside, and corre- 
sponding impressions without; diameter 13. W. 
33. 30. 
C. GUALTERIANA. Imperforate, flat above, 
convexly turgid, beneath rough, decussated, dirty 
ash-colour; spire extremely flat; lip thin and 
reflected ; diameter 12. W. 33. 44. 
C. MaRGINATA. Umbilicated, obliquely stri- 
ated, and the spire depressed; base convex, and 
the aperture ear-shaped, with a white margin ; 
